37 research outputs found
Polarization of Cosmic Microwave Background
In this work we present an extension of the ROMA map-making code for data
analysis of Cosmic Microwave Background polarization, with particular attention
given to the inflationary polarization B-modes. The new algorithm takes into
account a possible cross-correlated noise component among the different
detectors of a CMB experiment. We tested the code on the observational data of
the BOOMERanG (2003) experiment and we show that we are provided with a better
estimate of the power spectra, in particular the error bars of the BB spectrum
are smaller up to 20% for low multipoles. We point out the general validity of
the new method. A possible future application is the LSPE balloon experiment,
devoted to the observation of polarization at large angular scales.Comment: 6 pages, 4 figures, proceedings of the 6th Young Researchers Meeting,
L'Aquila, Oct 12th-14th 201
Optimal strategy for polarization modulation in the LSPE-SWIPE experiment
CMB B-mode experiments are required to control systematic effects with an
unprecedented level of accuracy. Polarization modulation by a half wave plate
(HWP) is a powerful technique able to mitigate a large number of the
instrumental systematics. Our goal is to optimize the polarization modulation
strategy of the upcoming LSPE-SWIPE balloon-borne experiment, devoted to the
accurate measurement of CMB polarization at large angular scales. We depart
from the nominal LSPE-SWIPE modulation strategy (HWP stepped every 60 s with a
telescope scanning at around 12 deg/s) and perform a thorough investigation of
a wide range of possible HWP schemes (either in stepped or continuously
spinning mode and at different azimuth telescope scan-speeds) in the frequency,
map and angular power spectrum domain. In addition, we probe the effect of
high-pass and band-pass filters of the data stream and explore the HWP response
in the minimal case of one detector for one operation day (critical for the
single-detector calibration process). We finally test the modulation
performance against typical HWP-induced systematics. Our analysis shows that
some stepped HWP schemes, either slowly rotating or combined with slow
telescope modulations, represent poor choices. Moreover, our results point out
that the nominal configuration may not be the most convenient choice. While a
large class of spinning designs provides comparable results in terms of pixel
angle coverage, map-making residuals and BB power spectrum standard deviations
with respect to the nominal strategy, we find that some specific configurations
(e.g., a rapidly spinning HWP with a slow gondola modulation) allow a more
efficient polarization recovery in more general real-case situations. Although
our simulations are specific to the LSPE-SWIPE mission, the general outcomes of
our analysis can be easily generalized to other CMB polarization experiments.Comment: 11 pages, 9 figures, accepted for publication in A&
Optimization of the half wave plate configuration for the LSPE-SWIPE experiment
The search for the B-mode polarization of Cosmic Microwave Background (CMB)
is the new frontier of observational Cosmology. A B-mode detection would give
an ultimate confirmation to the existence of a primordial Gravitational Wave
(GW) background as predicted in the inflationary scenario. Several experiments
have been designed or planned to observe B-modes. In this work we focus on the
forthcoming Large Scale Polarization Explorer (LSPE) experiment, that will be
devoted to the accurate measurement of CMB polarization at large angular
scales. LSPE consists of a balloon-borne bolometric instrument, the Short
Wavelength Instrument for the Polarization Explorer (SWIPE), and a ground-based
coherent polarimeter array, the STRatospheric Italian Polarimeter (STRIP).
SWIPE will employ a rotating Half Wave Plate (HWP) polarization modulator to
mitigate the systematic effects due to instrumental non-idealities. We present
here preliminary forecasts aimed at optimizing the HWP configuration.Comment: 6 pages, 4 figures, proceedings of the 7th Young Researcher Meeting,
Torino, Oct 24th-26th 201
How the Universe got its Spots
The universe displays a three-dimensional pattern of hot and cold spots in
the radiation remnant from the big bang. The global geometry of the universe
can be revealed in the spatial distribution of these spots. In a topologically
compact universe, distinctive patterns are especially prominent in spatial
correlations of the radiation temperature. Whereas these patterns are usually
washed out in statistical averages, we propose a scheme which uses the
universe's spots to observe global geometry in a manner analogous to the use of
multiple images of a gravitationally lensed quasar to study the geometry of the
lens. To demonstrate how the geometry of space forms patterns in observations
of the microwave sky, we develop a simple real-space approximation to estimate
temperature correlations for any set of cosmological parameters and any global
geometry. We present correlated spheres which clearly show geometric pattern
formation for compact flat universes as well as for the compact negatively
curved space introduced by Weeks and another discovered by Best. These examples
illustrate how future satellite-based observations of the microwave background
can determine the full geometry of the universe.Comment: 16 pages, 26 figure
Energy Density, Temperature and Entropy Dynamics in Perturbative Reheating
We discuss the perturbative decay of the energy density of a non standard
inflaton field and the corresponding creation of the energy
density of the relativistic fields at the end of inflation, in the
perfect fluid description, refining some concepts and providing some new
computations. In particular, the process is characterized by two fundamental
time scales. The first one, , occurs when the energy density
reaches its largest value, slightly after the beginning of the
reheating phase. The second one, , is the time in which the
reheating is completely realized and the thermalization is attained. By
assuming a non-instantaneous reheating phase, we are able to derive the energy
densities and the temperatures of the produced relativistic bath at
and , as well as the value of the corresponding
horizon entropy , for an Equation-of-State (EoS) parameter .Comment: Compatible with the published PRD Version - 11 pages, 6 figure
CAESAR: Space Weather archive prototype for ASPIS
The project CAESAR (Comprehensive spAce wEather Studies for the ASPIS
prototype Realization) is aimed to tackle all the relevant aspects of Space
Weather (SWE) and realize the prototype of the scientific data centre for Space
Weather of the Italian Space Agency (ASI) called ASPIS (ASI SPace Weather
InfraStructure). This contribution is meant to bring attention upon the first
steps in the development of the CAESAR prototype for ASPIS and will focus on
the activities of the Node 2000 of CAESAR, the set of Work Packages dedicated
to the technical design and implementation of the CAESAR ASPIS archive
prototype. The product specifications of the intended resources that will form
the archive, functional and system requirements gathered as first steps to seed
the design of the prototype infrastructure, and evaluation of existing
frameworks, tools and standards, will be presented as well as the status of the
project in its initial stage.Comment: 4 pages, 2 figures, ADASS XXXII (2022) Proceeding
Parameter distributions for the drag-based modeling of CME propagation
In recent years, ensemble modeling has been widely employed in space weather to estimate uncertainties in forecasts. We here focus on the ensemble modeling of Coronal Mass Ejections (CME) arrival times and arrival velocities using a drag-based model, which is well-suited for this purpose due to its simplicity and low computational cost. Although ensemble techniques have previously been applied to the drag-based model, it is still not clear how to best determine distributions for its input parameters, namely the drag parameter and the solar wind speed. The aim of this work is to evaluate statistical distributions for these model parameters starting from a list of past CME-ICME events. We employ LASCO coronagraph observations to measure initial CME position and speed, and in situ data to associate them with an arrival date and arrival speed. For each event we ran a statistical procedure to invert the model equations, producing parameters distributions as output. Our results indicate that the distributions employed in previous works were appropriately selected, even though they were based on restricted samples and heuristic considerations. On the other hand, possible refinements to the current method are also identified, such as the dependence of the drag parameter distribution on the CME being accelerated or decelerated by the solar wind, which deserve further investigation
Constraints on Primordial Non-Gaussianity from a Needlet Analysis of the WMAP-5 Data
We look for a non-Gaussian signal in the WMAP 5-year temperature anisotropy
maps by performing a needlet-based data analysis. We use the foreground-reduced
maps obtained by the WMAP team through the optimal combination of the W, V and
Q channels, and perform realistic non-Gaussian simulations in order to
constrain the non-linear coupling parameter \fnl. We apply a third-order
estimator of the needlet coefficients skewness and compute the
statistics of its distribution. We obtain -80<\fnl<120 at 95% confidence
level, which is consistent with a Gaussian distribution and comparable to
previous constraints on the non-linear coupling. We then develop an estimator
of \fnl based on the same simulations and we find consistent constraints on
primordial non-Gaussianity. We finally compute the three point correlation
function in needlet space: the constraints on \fnl improve to -50<\fnl<110
at 95% confidence level.Comment: 9 pages, 6 figures. MNRAS in press, updated to accepted versio
Exploring Cosmic Origins with CORE: Cosmological Parameters
We forecast the main cosmological parameter constraints achievable with theCORE space mission which is dedicated to mapping the polarisation of the CosmicMicrowave Background (CMB). CORE was recently submitted in response to ESA'sfifth call for medium-sized mission proposals (M5). Here we report the resultsfrom our pre-submission study of the impact of various instrumental options, inparticular the telescope size and sensitivity level, and review the great,transformative potential of the mission as proposed. Specifically, we assessthe impact on a broad range of fundamental parameters of our Universe as afunction of the expected CMB characteristics, with other papers in the seriesfocusing on controlling astrophysical and instrumental residual systematics. Inthis paper, we assume that only a few central CORE frequency channels areusable for our purpose, all others being devoted to the cleaning ofastrophysical contaminants. On the theoretical side, we assume LCDM as ourgeneral framework and quantify the improvement provided by CORE over thecurrent constraints from the Planck 2015 release. We also study the jointsensitivity of CORE and of future Baryon Acoustic Oscillation and Large ScaleStructure experiments like DESI and Euclid. Specific constraints on the physicsof inflation are presented in another paper of the series. In addition to thesix parameters of the base LCDM, which describe the matter content of aspatially flat universe with adiabatic and scalar primordial fluctuations frominflation, we derive the precision achievable on parameters like thosedescribing curvature, neutrino physics, extra light relics, primordial heliumabundance, dark matter annihilation, recombination physics, variation offundamental constants, dark energy, modified gravity, reionization and cosmicbirefringence. (ABRIDGED